1. Technical Field
The invention relates to an input switching apparatus and an input switching method of an audio/video signal for selecting one of a plurality of audio/video signals and reproducing or outputting the same from an output unit, and an audio/video system.
2. Background Art
As a technology of transmitting an audio/video signal (AV signal) between a source device and a sink device in a digital format, an HDMI (High-Definition Multimedia Interface) has been put to practical use. As an optional function of the HDMI, there is a CEC (Consumer Electronics Control) function for interconnection operation between home electric appliances. An interconnection operation function using the CED such as one-touch play, remote control pass-through and system standby has been implemented.
The HDMI has a variety of lines of transmitting and receiving a control signal, in addition to a TMDS (Transition Minimized Differential Signaling) line of transmitting an AV stream signal. The lines include a CEC line that transmits a CEC message. In an AV device having a plurality of HDMI input terminals, the TMDS line becomes active only in a selected path and transmits an AV signal in one direction from a source device to a sink device. However, the CEC line is connected to all devices including a device that is not selected, in a tree structure, and the devices interactively perform communication while distinguishing the devices each other by address information attached to the CEC message. In the meantime, an AV device having a plurality of HDMI input terminals and having a function of selecting one of the HDMI input terminals is referred to as a CEC switch. In an AV system, an AV amplifier, a television receiver and the like have the function of the CEC switch.
A function of the CEC is described with reference to FIG. 1. FIG. 1 shows an example of an AV system including a CEC switch. An AV amplifier 500 having a switching function is connected with a television receiver 501 serving as a sink device, and with a DVD player 502 and a set-top box (STB) 503 serving as source devices. The AV amplifier 500 has a function of selecting one of a plurality of inputs (in this example, the DVD player 502 and the set-top box 503) and outputting the same to the television receiver 501 and corresponds to a CEC switch.
In the AV system having the above connection topology, when a play switch of the DVD player 502 becomes on, the DVD player 502 outputs a CEC message (Active Source message), so that the AV amplifier 500 switches the input to the DVD player 502. Also, when a power supply of the set-top box 503 becomes on, the CEC message (Active Source message) is output from the set-top box 503, so that the AV amplifier 500 switches the input to the set-top box 503. In the meantime, JP-A-2008-054300 discloses a technology of such HDMI connection.